Pull-ups and chin-ups work nearly all the same muscles, but they load those muscles in different proportions. Both exercises target the large back muscles, the biceps, and the shoulders. The key difference is grip: pull-ups use an overhand (palms facing away) grip, while chin-ups use an underhand (palms facing you) grip. That single change in hand position shifts how much work each muscle group contributes to the movement.
The Muscles Both Exercises Share
Every pull-up and chin-up repetition requires your lats (the broad muscles running down each side of your back), your biceps, your trapezius, your rear deltoids, and the smaller elbow flexors in your upper arm. The lats do the heavy lifting in both variations, pulling your body upward by drawing your upper arms down toward your torso. The biceps and other elbow flexors bend your arms to complete the pull. No matter which grip you choose, you’re training all of these muscles through a large range of motion.
The elbow moves through roughly 93 to 101 degrees during a full rep, depending on the variation. Chin-ups tend to use slightly more elbow range of motion (about 101 degrees on average) compared to pull-ups (about 93 degrees), which means the arm flexors work through a somewhat longer path during chin-ups.
How Grip Changes Muscle Emphasis
Rotating your forearm from an overhand to an underhand position changes the mechanical advantage of several muscles at the elbow. When your palms face you during a chin-up, the biceps sit in a stronger pulling position relative to the forearm bone. This lets them contribute more force to the movement. That extra biceps involvement is why most people find chin-ups easier than pull-ups, and why they can typically complete more reps or add more weight with an underhand grip.
When your palms face away during a pull-up, the biceps lose some of that mechanical advantage. The body compensates by relying more heavily on the brachioradialis, a forearm muscle that runs from just above the elbow to the wrist. The brachioradialis picks up slack during pull-ups because the overhand grip puts the biceps in a weaker position. However, even at its best, the brachioradialis never achieves an ideal pulling angle (it stays below 45 degrees relative to the forearm), so it’s inherently less efficient than the biceps as an elbow flexor. This is a major reason pull-ups feel harder.
There’s also the brachialis, a deep muscle underneath the biceps. It flexes the elbow regardless of how your forearm is rotated, so it contributes steadily to both exercises. When the biceps and brachioradialis are both at a disadvantage, the brachialis becomes even more important as a stabilizer and force producer.
What Happens in the Back and Shoulders
The lats are the primary mover in both exercises. Pull-ups, with their wider overhand grip, tend to place a greater demand on the lats because they receive less assistance from the biceps. This doesn’t mean chin-ups skip the lats. Both variations produce high levels of lat activation. But the pull-up’s grip essentially forces the back to work harder to compensate for what the arms can’t provide.
The mid-trapezius and rear deltoids fire during both movements as you squeeze your shoulder blades together at the top of each rep. EMG data from pull-up studies shows the posterior deltoid can actually produce very high activation levels, sometimes exceeding 100% of its baseline maximum voluntary contraction. The rhomboids, which sit between your shoulder blades, also work during both variations to retract the scapula.
Which Variation Is Harder
Most people can do more chin-ups than pull-ups. The reason is straightforward: the underhand grip recruits the biceps more effectively, giving you an extra source of pulling power that the overhand grip partially takes away. The pull-up compensates by leaning on the brachioradialis and demanding more from the lats, but that trade isn’t equal. The brachioradialis is a smaller, mechanically weaker elbow flexor compared to the biceps.
If you’re newer to pulling exercises, chin-ups are often a better starting point. If you can already do multiple chin-ups and want to challenge your back more directly, switching to pull-ups increases the difficulty without needing added weight.
Joint Stress Differences
The two grips create different loading patterns at the shoulder and elbow. Research examining rotator cuff loading across pull-up techniques found that reverse (underhand) grip pull-ups displayed higher proportional rotator cuff activation compared to standard overhand pull-ups. This doesn’t automatically mean chin-ups are riskier for your shoulders, but it does mean the small stabilizing muscles around the shoulder joint work harder during the underhand variation.
At the elbow, chin-ups place more stress on the inner side of the joint because the biceps pull forcefully in a supinated position. People who do high volumes of chin-ups sometimes develop irritation on the inside of the elbow, similar to what’s sometimes called golfer’s elbow. Pull-ups shift more of that stress to the outer forearm and the brachioradialis, which can contribute to outer elbow discomfort in some people. Alternating between both grips over time helps distribute stress across different tissues rather than overloading one area.
Choosing Between Them
If your goal is overall upper-body pulling strength, both exercises deliver. The practical differences come down to emphasis:
- Chin-ups are better for biceps development and are generally easier to progress because the stronger grip position lets you do more reps or add load sooner.
- Pull-ups place more demand on the lats and brachioradialis, making them a slightly better choice if your priority is back width and you want to reduce how much the biceps can take over.
Including both in your training is the simplest solution. They use the same equipment, target the same muscle groups, and the grip differences are just enough to provide variety in how those muscles are loaded. You could alternate between them across sessions, or use one as your primary movement and the other as an accessory. Either way, the muscles worked overlap heavily. The real distinction is which muscles lead the effort and which ones play a supporting role.